Drying time recorder



April 21, 1942.

P. N GARDNER DRYING TIME RECORDER,

Filed oct. 51, 1941 Patented Apr. 21, 1942 DRYING TIME RECORDER K y Paul Norris Gardner, Bethesda, Md. Application October 31, 1941,v Serial N o. 417,409

8 Claims.-

'Ihis invention relates to the art of determining and recording the speed of setting, hardening or drying of plastic compositions, and is concerned with improvements in devices for use in said art. More particularly, the invention involves improvements in an apparatus for, and method of, determining the speed of drying of paints, enamels, varnishes and similar lmforming compositions: the improved apparatus also is adaptable for use in determining and recording the setting and hardening times of plastic masses, cementitious mixtures and other compositions which set from a soft plastic state toa hard or relatively. stone-like state.

In essence, the improved apparatus of the present invention comprises a movable elongated table for supporting a test strip or layer, a rigid contacting member in the form of a freely rotatable rigid toothed Wheel of' predetermined weight, said rigid contacting toothed wheel being sojournaled .as to be free to move vertically and having a circumference substantially equal to the 4effective length of the movable table, and means for moving the table lengthwise, in one direction, beneath and in supporting relation to the rigidv contacting toothedwheel at a prede.-

termined and constant rate of Vspeed so that each unit of lengthwise movement of the table represents a definite. time interval. The device preferably is formed'to be used on a substantially iiat laboratoryvbench or table.

The movable table,which has a at test strip- (or layer) (supporting surface, preferably is supported in-aA substantially horizontal plane by means of vertically adjustable castorsl or equivalent rolling supports positioned adjacent the ends of the table. The table may be adapted to support a single test strip or layer, or a plurality of the same disposed side by side. yIt may be, and if plastic layers are to be tested, preferably is, Vprovided with upwardly anged. side C;

portions. While it is possible to mount the material to be tested directly onl the supporting surface of the table, I. prefer to have the test material deposited` on thin supporting strips which may be removably fastened to the table surface for the test and thereafter removed to constitute a permanent record of the test. Accordingly, I prefer to equip the movable tablelwith suitable strip holding devices, e. g., spring clips,

f; or of suitably prepared and sized paper or similar flat web material. The strips may, if desired,"bear any Wanted indicia, e. g., indicia of linear .distance, or of time, or the like.

On the underside of the table there is 'provided a toothed rack preferably extending from and with suitablecentering and retaining devices, e. g., pins, for maintaining the test .strips in predetermined positions on the movable table. The test strips may be formed of thin sheet metal (preferably tin-plated thin sheet steel) endv to end thereof the rack meshes with a pinion mounted on a drive shaft. journalled between upright 'supporting members which latter may mount the bearings for the axle of the contacting Wheel.vr 'I'he pinion drive shaft is connected in conventional'manner with a suitable constant speed. motor such, for instance, `as a clock mechanism, a small electric motor, or the like. The speed of, the motor and the size of the pinion are, so selected that the table and supported test strips may be caused to move at the rate of, say, one and one-sixth inches per hour, although slower or faster speeds may be introduced, in knownmanner, by suitable alterationof the diameter of the pinion and/or alteration of the motor speed. `lThe motor may if udesired bej housed in any suitable manner. The contacting toothed wheel is mounted on an axle which, when thedevice is in use, is substantiallyhorizontal and transverse to the direction of travelof the table. The axle is journalled lin vertical channel bearings which permit free rotation of the axle and free vertical movement of the, latter While holding it against lateral movement. contacting toothed wheel may (as where the 'device is to be employed for determining and recording the setting and drying times of a paint or the like) may be formed asgear teeth having rectilinear faces, or they may (as where the device is to beemployed for testing cementitious mixtures or equivalent plastic masses) be formed as relatively sharp spikes. The weight of the contacting toothed wheel is to be determined by the vtype of testing.inv/hieltl the device is to be used: it maybe formed to a predetermined weight, o r it maybe formed asl a spokedwheel adapted to be fttedwith weights as desired.l

According to a preferred Vembodiment ofthe i invention, the movable table is adapted to support a pair of test strips (e. g., an unknown Vand a control), and 'a pair` of contacting toothed'wheels are mounted on the wheel axle in such manner that eachwheel contacts a sin- 'gle test strip. In this embodiment, the device is adapted to determine and record the setting and, drying .times of a paint (or equivalent) Vsample and ysimultaneously. to check that test against aT control sample of .known setting yand The teeth` of the 'l drying times,-in order to overcome inaccuracies occasioned by extraordinary atmospheric conditions obtaining at the time of the particular test.

The operation of the device will now be described with particular reference to the testing of a paint iilm of unknown setting and drying times against a control of known characteristics, and using removable test strips for supporting the painthns: f

A uniform iilm, say of about .003" thickness, of the paint to be tested is applied, as by means of known iinal-coating devices or gauges, to the tinned test strip, and a layer, of the same thickness, of the control paint is applied to a like test strip. These freshly coated test strips'arethose clipped onto the strip-supportingsurface of the movable table, the forward end of the table is mounted on the pinion, the pinion-drivingmechanism isset in operation: (so. that the. table and supported .test .strips start; slowly` to. move) and the a-xle carrying. the contactingtoothed lwheels is slippedlintof-its 4channel bearings.. so that the Wheels press finto Athe fresh coatings. on. the test strips Asthe table and supported test strips move, the contacting toothed wheels. are caused to rotate, `the teeth of the contacting toothed wheels successivelyv bearing the. weight. of.' their respective Wheelsupon the wet. paint. lr'ns. That -weight.(e. g., approximatelylgrams in a particular example) is Y such .that at rst i the teeth pressthroughthe wetiilms. and-pickup portions of the films upon theirY surfaces, ex-

posing the brightmetal. surfaces of the tinned strips where the teeth have impnged thereupon. The paintlms `usually, continue to remain wet for from two. to eightfhours. (depending. of course on the Vspeedfof dryingof Vtllecornposition) after theirr application; and the. impressions.. of.v the .teetl'rxthrough the lms: and downrto the. bare metal will be visible-for alike period. I-.f call the end of this period -theffset to touchtime.

Asfsoon as the paintiilmshave-takenup suffisively resists indentation by the spikes of the wheel so that the depressions (made by the spikes) progressively become shallower and shallower until they fade out altogether and the Wheel rides upon the surface of the test layer.

It is to be understood that a single test (be it of paint, or cementitious mixture, or other plastic composition) may be made, with a single contacting toothed wheel. It is to be understood, also, that it is within the scope of the invention to modify the device in such manner that the pinion drive shaft is suciently extended (from the motor) to mount a plurality of spaced drivingpinions, that a plurality of movable tables (each bearing one or a plurality of test strips) are" actuated by said pinions, and that a pluvrality of axled contacting toothed wheels are cient oxygen (or,-have otherwise alterecltheir properties) to have: become. thickened'v orr gelled, the successively contactedfteethnolonger remove portions'ofthe paint-.filmslfromthe teststrips, ,but-merely travel over the surfaces of theY films leaving-'surface indentations inlthelatter. Ica-ll the end.of this period the tack-freey time. At such furtherv timeintervalsas the. paint films become finally hardened the successively; contacted'teeth no longer makeimpressions in the fllmsz-this latter'paint IY call thefharddry time. The lilmed'teststrips-bear` permanent direct reeordsof the courses of these several periods, and, desirably, these recordsiareinterpreted. by

time or* distance indicia' along an edge of each test strip. y

In adapting-.the Yabovespecifically described devicefor use. iny determining and recording the setti-ngtime of a-cementitious mixture (e. gf., a Portland cementmix) I substitute .for the cogged Wheel one, of suitable Weight, bearing. sharp spi-kesealongf itszperiphery, and -I-substitute :a tray Yfor the test-supporting` strips.- Inoperatingthe soeadapted device,.the tray is .'lledwith a from one-fourth inchv to one inch layerfof the: freshly prepared cementitiousmixture andisxedtothe moving table, the driving mechanismris started, and the spiked Wheell is placed in position. As the table and supported tray slowly move forward',the spikes at rst penetrate into they mixture. under test', leaving .deep indentations therein; thereafter as the mixture setsf it progresemployed, in a plurality of pairs of vertically floating channel bearings, above said movable tables The invention will now bedescribed 'ingreater detailand' with reference to the accompanying drawing.' in which Fig. .1' is a. plan view ofA a complete apparatus accordingto the invention, with a test' strip and acontrol strip in place' therein;v

Fig. 2 lisa side elevation', with parts insection, of the apparatus shownin 1';

Fig. 3 is a plan .vievvof a test'st'rip illustrating the recordation of 'a drying timetestv madeton a layer of film-forming coatingjcomposition (e. g., paint); and f Fig. 4'is afragmentaryperspective view illustrating a modification fof ,partsbf the' complete apparatus of Fig. 1'.

In Figs. 1.and.2, the movable elongated'table I is shown Vas beingadapted to support a pair, of test strips` 4, 4'.. 'I'hetableissupportedfon verti cally; adjustable Acastors .-2, 2 It is -providedwitli upstanding flange portions 3, 3, along itssides. Metal. test strips. 4, 4" (one strip 4 being, inthis case, the unknown and the. other the control strip) are lsecured.to.-the upper surface of table I by a pair of 'sprihgclips 55, attached to the table at oneend tlfrereof: spacedpins-B, 6; are disposed in the table top for aligning.the test strips onthe table. v. J

Attached to the,undersurface of table I is a rack 1 which extends substantially from endto end of the table. i 8'is a pinion, mounted on drive shaft 9, adapted to engage rack 'I and thereby to move table I from right to left. Drive shaft 9 is connected to a clock-Work motor,.diagram matically represented. by housing IU,.as driving mechanism forthe apparatus.

The'rigid contacting member is represented in Figs. 1 and 2 by two spoked gear Wheels I I, II, mounted on a common axle I2. Axle I'2'is'free to rotate and to move vertically, but is heldagainst longitudinal movement by two.vertical channel bearings. I3, I3. As shown, one channel bearingl 3 is secured to motor housing I0, and the yother is secured to a.face of 'vertical supportingmember I4. Supporting member Illismountedy on flanged baseIS which latter. may be, and preferably is, secured to motor housingl 0,

Each gear wheel. II is constructed to have a periphery substantially corresponding to the length of teststrip 4. The gear teeth are provided with rectilinear peripheral faces I 6,. IG.,

and the otherL test strip 4 is likewise coated with a layer of the paint to be tested. The freshly coated strips d, 4, are'immediately mounted on' ation of the clock-work' motor. As soon as'the mechanism is started in` operation, the axle I2 of the pair of wheels II, I I, is slipped into place in channel bearings I3, I3, and Wheels II, II are permitted to restupon the freshly coated test strips 4, 4.

The teeth of wheels II, I I, sink through the layers of paint and directly contact the bright surfaces of strips 4, "I, Movement/of table I serves to rotate Wheels I I, I I, and, at the outset of the test, the teeth of the latter successively pick up paint from the strips, making a series of rectilinear markings I6', I6 in the respective coat ing layers. As the test progresses, exposure of the bare metal in markings I6', I6' becomes less and less, and eventually ceases. This point (the set to touch time) is represented at A in Fig. 3, opposite the indicia representing 4 inches of travel of the strip (say, 4 and 2/3 hours of test). Point B represents the end of the tack-free period, and became manifest after the strip had traveled 8 inches. Point C represents the hard dry time of the test, and appeared after the strip had traveled 12 inches.

After the test has been run, and the driving mechanism stopped, wheels I I, I I, are lifted from their bearings, and the strips 4, 4, are removed from clips 5, 5, and either stored as permanent records of the test or cleaned for subsequent testing use.

It is to be understood that table I may be adapted to support but a single test strip, in which event but a single wheel I I is mounted on axle I2; or, it may be adapted to support more than two test strips, in which event as many wheels II are mounted on axle I2 as there are test strips.

It is to be understood, also, that the apparatus may be expanded by adding a further support I4 and base I5, extending drive shaft 9, as by a series of unknown-control tests simultaneously may be run off, using a single driving mechanism.

For determining, or determining and record, the setting time of a freshly prepared Portland cement mix (or plaster, or putty or similar composition which is freely plastic as prepared but sets to a relatively stone-like state), the apparatus of Figs. 1 and 2 is modified, as shown in Fig. 4, by substituting a trough I8 for iiat test strip Il, for containing the plastic mass I9, and by substituting for gear wheel II a Wheel 20 provided over its periphery with regularly spaced sharpended spikes 2l, 2l. In using this modified apparatus, spikes 2| at first pierce the mass IS and engage trough I8; movement of the table, and hence of trough I8, causes the successive piercing of mass I9 by spikes 2|, 2l, leaving in the mass their indentations 2l'. As the mass I9 sets, indentations 2 I fade out and eventually disappear, marking the setting time of the mass being tested.

I claim:

1. Apparatus for determining and recording the setting, hardening or drying time of a plastic composition such as a paint, a cementitious mix or the like, which comprises a movable elongated table for supporting a test layer, a rigid contacting member in the form of ajf'reely `rotatable Wheel on the periphery of which are spacedlprotuberances, said Wheel being journaledto be free to rotate and to move vertically and being adapted to rest peripherally on saidjtalola'V and means for advancing the table beneath" said wheel, and with the weight of said-Wheel resting thereon, at constant speed. f 1

Apparatus nfor ,determining and recording the setting, hardening or drying time of a plastic composition such as a paint, a cementitious-mix or the like, which comprises amovable elongated table for supporting a test layer, a rack attached to the table, a co-operating pinion in mesh with said rack, means for rotating the pinion at constant speed, and a rigid contacting member in the form of a freely rotatable Wheel on the periphery of which are spaced protuberances, said Wheel having a circumference substantially corresponding to the effective length of said table, and being journaled to be free to rotate and to move vertically and being adapted to rest peripherally on said table.

3. Apparatus for determining and recording the setting, hardening or drying time of a plastic composition such as a paint, a cementitious mix or the like, which comprises a movable elongated table for supporting a test layer, a rack attached to the under surface of the table, `a pinion4 mounted on a drive shaft, said pinion being adapted to mesh with said rack, means for rotating the drive shaft at constant speed, and a rigid contacting member in the form of a freely rotatable wheel on the periphery of which are spaced protuberances, said Wheel having a circumference substantially corresponding to the effective length of said table, and being journaled to be free to rotate and to move vertically and being adapted to rest peripherally on said table.

4. The apparatus defined in claim 1, in which the protuberances are gear teeth presenting substantially plane peripheral surfaces.

5. The apparatus defined in claim 1, in which the protuberances are gear teeth presenting rectilinear peripheral surfaces.

6. The apparatus defined in claim l, in Which the protuberances are relatively sharp-ended spikes. v

'7. Apparatus for determining and recording the setting, hardening or drying time of a plastic composition such as a paint, a cementitious mix or the like, which comprises a movable elongated table for supporting a test layer, a removable test strip for carrying a test layer of the material to be tested, said strip being adapted to be supported on theupper surface of said table, means for removably securing said test strip lengthwise on said. table, a rigid contacting member in the form of a freely rotatable Wheel on the periphery of which are spaced protuberances, said wheel being journaled to be free to rotate and to move vertically and being adapted to rest peripherally on said test strip on said table, and means for advancing the table and teststrip beneath said wheel, and with the weight of said Wheel resting thereon, at constant speed.

8. Apparatus for determining and recording the setting, hardening or drying time of a plastic composition such as a paint, a cementitious mix or the like, and for comparing such time with that of a control sample, of known setting, hardening or drying time, under identical conditions of test, which comprises a movable elongated table adapted to support a pair of test strips thereon, a pair of elongated removable test for"aligningthesameY in spaced parallel krelation on said table,V a rack attached .to the .under surface ofsaidftable, a vcooperating pinionin mesh with saidrack andi mounted` on adrive shaft, means for rotating theV driveshafty at constant speed, a pair of substantially vertical open-ended channel bearings on either side of and above said table, an axle adapted, freely to rotateand to move verticallyin said bearings above andtransstripsusupported; on said fiable; meansflfor'remov- Y ably.t securing;y said,` test strips lengthwise; to; and v PAUL NORRIS GARDNER. 

